Pursuant to 37 C.F.R. 1.71(e), Applicants note that a portion of this disclosure contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
The present invention relates to new polypeptides exhibiting granulocyte colony-stimulating factor (G-CSF) activity, to conjugates between a polypeptide exhibiting G-CSF activity and a non-polypeptide moiety, to methods for preparing such polypeptides or conjugates and the use of such polypeptides or conjugates in therapy, in particular for the treatment of leukopenia.
The process by which white blood cells grow, divide and differentiate in the bone marrow is called hematopoiesis (Dexter and Spooncer, Ann, Rev. Cell. Biol., 3:423, 1987). Each of the blood cell types arises from pluripotent stem cells. There are generally three classes of blood cells produced in vivo: red blood cells (erythrocytes), platelets and white blood cells (leukocytes), the majority of the latter being involved in host immune defence. Proliferation and differentiation of hematopoietic precursor cells are regulated by a family of cytokines, including colony-stimulating factors (CSF""s) such as G-CSF and interleukins (Arai et al., Ann. Rev. Biochem., 59:783-836, 1990). The principal biological effect of G-CSF in vivo is to stimulate the growth and development of certain white blood cells known as neutrophilic granulocytes or neutrophils (Welte et al., PNAS-USA 82:1526-1530, 1985, Souza et al., Science, 232:61-65, 1986). When released into the blood stream, neutrophilic granulocytes function to fight bacterial infection.
The amino acid sequence of human G-CSF (hG-CSF) was reported by Nagata et al. Nature 319:415-418, 1986. hG-CSF is a monomeric protein that dimerizes the G-CSF receptor by formation of a 2:2 complex of 2 G-CSF molecules and 2 receptors (Horan et al. (1996), Biochemistry 35(15): 4886-96). Aritomi et al. Nature 401:713-717, 1999 have described the X-ray structure of a complex between hG-CSF and the BN-BC domains of the G-CSF receptor. They identify the following hG-CSF residues as being part of the receptor binding interfaces: G4, P5, A6, S7, S8, L9, P10, Q11, S12, L15, K16, E19, Q20, L108, D109, D112, T115, T116, Q119, E122, E123, and L124. Expression of rhG-CSF in Escherichia coli, Saccharomyces cerevisiae and mammalian cells has been reported (Souza et al., Science 232:61-65, 1986, Nagata et al., Nature 319: 415-418, 1986, Robinson and Wittrup, Biotechnol. Prog. 11:171-177, 1985).
Recombinant human G-CSF (rhG-CSF) is generally used for treating various forms of leukopenia. Thus, commercial preparations of rhG-CSF are available under the names filgrastim (Gran(copyright) and Neupogen(copyright)), lenograstim (Neutrogin(copyright) and Granocyte(copyright)) and nartograstim (Neu-up(copyright)). Gran(copyright) and Neupogen(copyright) are non-glycosylated and produced in recombinant E. coli cells. Neutrogin(copyright) and Granocyte(copyright) are glycosylated and produced in recombinant CHO cells and Neu-up(copyright) is non-glycosylated with five amino acids substituted at the N-terminal region of intact rhG-CSF produced in recombinant E. coli cells.
A few protein-engineered variants of hG-CSF have been reported (U.S. Pat. No. 5,581,476, U.S. 5,214,132, U.S. 5,362,853, U.S. 4,904,584 and Riedhaar-Olson et al. Biochemistry 35: 9034-9041, 1996). Modification of hG-CSF and other polypeptides so as to introduce at least one additional carbohydrate chain as compared to the native polypeptide has been suggested (U.S. Pat. No. 5,218,092). It is stated that the amino acid sequence of the polypeptide may be modified by amino acid substitution, amino acid deletion or amino acid insertion so as to effect addition of an additional carbohydrate chain. In addition, polymer modifications of native hG-CSF, including attachment of PEG groups, have been reported (Satake-Ishikawa et al., Cell Structure and Function 17:157-160, 1992, U.S. Pat. No. 5,824,778, U.S. 5,824,784, WO 96/11953, WO 95/21629, WO 94/20069).
Bowen et al., Experimental Hematology 27 (1999), 425-432 disclose a study of the relationship between molecule mass and duration of activity of PEG-conjugated G-CSF mutein. An apparent inverse correlation was suggested between molecular weight of the PEG moieties conjugated to the protein and in vitro activity, whereas in vivo activities increased with increasing molecular weight. It is speculated that a lower affinity of the conjugates act to increase the half-life, because receptor-mediated endocytosis is an important mechanism regulating levels of hematopoietic growth factors.
The commercially available rhG-CSF has a short-term pharmacological effect and must often be administered more once a day for the duration of the leukopenic state. A molecule with a longer circulation half-life would decrease the number of administrations necessary to alleviate the leukopenia and prevent consequent infections. Another problem with currently available RG-CSF products is the occurrence of dose-dependent bone pain. Since bone pain is experienced by patients as a significant side effect of treatment with rG-CSF, it would be desirable to provide a rG-CSF product that does not cause bone pain, either by means of a product that inherently does not have this effect or that is effective in a sufficiently small dose that no bone pain is caused. Thus, there is clearly a need for improved recombinant G-CSF-like molecules.
With respect to the half-life, one way to increase the circulation half-life of a protein is to ensure that clearance of the protein, in particular via renal clearance and receptor-mediated clearance, is reduced. This may be achieved by conjugating the protein to a chemical moiety which is capable of increasing the apparent size, thereby reducing renal clearance and increasing the in vivo half-life. Furthermore, attachment of a chemical moiety to the protein may effectively block proteolytic enzymes from physical contact with the protein, thus preventing degradation by non-specific proteolysis. Polyethylene glycol (PEG) is one such chemical moiety that has been used in the preparation of therapeutic protein products. A G-CSF molecule modified with a single, N-terminally linked PEG group, termed SD/01, is currently undergoing clinical trial. Although this PEGylated G-CSF molecule has been shown to have an increased half-life compared to non-PEGylated G-CSF, it has a low activity and must therefore be administered in rather high doses. As a result, the problem of bone pain discussed above has not been solved by this molecule. Furthermore, there is still substantial room for improvement of the known G-CSF molecules in terms of half-life.
A need therefore still exists for providing novel molecules exhibiting G-CSF activity that are useful in the treatment of leukopenia, and which have are improved in terms of an increased half-life and a reduction in side effects. The present invention relates to such molecules.
More specifically, the present invention relates to specific conjugates comprising a polypeptide exhibiting G-CSF activity and a non-polypeptide moiety, methods for their preparation and their use in medical treatment and in the preparation of pharmaceuticals. Accordingly, in a first aspect the invention relates to various specific conjugates comprising a polypeptide exhibiting G-CSF activity and having an amino acid sequence that differs from the known amino acid sequence of human G-CSF as shown in SEQ ID NO:1 in at least one specified altered amino acid residue comprising an attachment group for a non-polypeptide moiety, and having at least one non-polypeptide moiety attached to an attachment group of the polypeptide. The conjugate of the present invention has one or more improved properties as compared to commercially available rhG-CSF, including increased functional in vivo half-life, increased serum half-life, reduced side effects, reduced immunogenicity and/or increased bioavailability. Consequently, medical treatment with a conjugate of the invention offers a number of advantages over the currently available G-CSF compounds.
In a further aspect the invention relates to polypeptides exhibiting G-CSF activity and which form part of a conjugate of the invention. The polypeptides of the invention are contemplated to be useful as such for therapeutic, diagnostic or other purposes, but find particular interest as intermediate products for the preparation of a conjugate of the invention.
In a further aspect the invention relates to a polypeptide conjugate comprising a polypeptide exhibiting G-CSF activity, which comprises an amino acid sequence that differs from the amino acid sequence of hG-CSF (with the amino acid sequence shown in SEQ ID NO:1) in at least one amino acid residue selected from an introduced or removed amino acid residue comprising an attachment group for a non-polypeptide moiety, and a sufficient number or type of non-polypeptide moieties to provide the conjugate with an increased half-life compared to known recombinant G-CSF products.
In still further aspects the invention relates to methods for preparing a conjugate of the invention, including nucleotide sequences encoding a polypeptide of the invention, expression vectors comprising such a nucleotide sequence, and host cells comprising such a nucleotide sequence or expression vector.
In final aspects the invention relates to a composition comprising a conjugate or polypeptide of the invention, a method for preparing a pharmaceutical composition, use of a conjugate or composition of the invention as a pharmaceutical, and a method of treating a mammal with such composition. In particular, the polypeptide, conjugate or composition of the invention may be used to prevent infection in cancer patients undergoing certain types of radiation therapy, chemotherapy, and bone marrow transplantations, to mobilize progenitor cells for collection in peripheral blood progenitor cell transplantations, for treatment of severe chronic or relative leukopenia, irrespective of cause, and to support treatment of patients with acute myeloid leukaemia. Additionally, the polypeptide, conjugate or composition of the invention may be used for treatment of AIDS or other immunodeficiency diseases as well as bacterial infections.